Front suspension with three ball joints for a vehicle

ABSTRACT

A suspension for a vehicle includes an upper A-arm and a lower A-arm. A leg with an axis is rotatably connected to both the upper A-arm and the lower A-arm. A mechanical link is rotatably connected to the leg so that movement of the mechanical link applies rotational force to the leg to cause the leg to rotate about the axis.

This application is a Continuation of U.S. patent application Ser. No.10/634,911, filed on Aug. 6, 2003, which is itself a DivisionalApplication of Ser. No. 09/877,214, now U.S. Pat. No. 6,655,487 filed onJun. 11, 2001. U.S. Pat. No. 6,655,487 is a Continuation-In-Part of Ser.No. 09/472,133 filed on Dec. 23, 1999, and claims priority to 60/230,432filed on Sep. 6, 2000, 60/237,384, filed on Oct. 4, 2000, 60/251,263,filed on Dec. 5, 2000, and Canadian Application No. 2,256,944 filed onDec. 23, 1998. All aforementioned applications and patents areincorporated herein by reference. This application also incorporates byreference U.S. patent application Ser. No. 09/472,134, entitled“SNOWMOBILE,” which was filed on Dec. 23, 1999.

FIELD OF THE INVENTION

The present invention concerns generally concerns the construction ofvehicles such as snowmobiles, all terrain vehicles (“ATVs”), and othersimilar vehicles. More specifically, the present invention concerns theconstruction of a front suspension with three-ball joints that areconnected to a support leg for the vehicle.

DESCRIPTION OF RELATED ART AND GENERAL BACKGROUND

Snowmobiles, ATVs, wheeled vehicles, and other related vehicles(hereinafter, “recreational vehicles,” although the appellation shouldnot be construed to be limited only to the vehicles or type of vehiclesdescribed herein) often function under similar operating conditions.Despite this, snowmobiles, ATVs, wheeled vehicles, and otherrecreational vehicles do not share a common design approach or acommonality of components. This is due, in large part, to the differentstresses and strains (mainly at the extremes) that the differentvehicles experience during routine operation.

As a general rule, the prior art includes few, if any, examples of acommon design approach to ATVs, wheeled vehicles, and snowmobiles.Primarily, this appears to be due to the fact that these vehicles weredesigned traditionally from radically different starting points. Forexample, there has not been a common design approach to the frontsuspensions that are incorporated into snowmobiles, ATVs, and otherwheeled vehicles even though there are common design parameters for eachof these types of vehicles.

In the case of snowmobiles, two front suspensions are well known in theart. The first is typically referred to as a “trailing arm suspension”and is commonly found on snowmobiles manufactured by Bombardier Inc. ofMontreal, Quebec, Canada. The second is known as a double A-armsuspension and is typically found on snowmobiles manufactured by ArcticCat of Thief River Falls, Minnesota, USA.

A prior art trailing arm front suspension is generally depicted in FIGS.1, 3, and 36. As illustrated in detail in FIG. 36, a trailing armsuspension 442 includes a trailing arm 444 (which is also referred to asa swing arm). Trailing arm 444 connects between a pivot 446, whichconnects to engine cradle 56, and a front leg 448. Front leg 448connects ski 20 to engine cradle 56. A shock absorber 450 connectsbetween engine cradle 56 and trailing arm 444 to dampen the forcesassociated with the travel of snowmobile 12 over uneven terrain.Steering control of snowmobile 12 is provided by a mechanical linkbetween skis 20 and handlebars 82.

A typical double A-arm suspension 452 is illustrated generally in FIGS.37-40. The illustration of double A-arm suspension 452 that is shown inFIGS. 37-38 was reproduced from U.S. Pat. No. 5,664,649, which purportson its face to be assigned to Arctic Cat. As shown, double A-armsuspension 452 includes an upper A-arm 454 and a lower A-arm 456. BothA-arms 456, 454 are connected to front leg 458 and permit front leg 458to move vertically as snowmobile 460 travels over uneven terrain. Ashock absorber 462, which is connected between the body of snowmobile460 and lower A-arm 456, dampens the forces applied to skis 464 assnowmobile 460 travels over the ground. Alternatively, it is known toconnect shock absorber 450 directly to front leg 458, as illustrated inFIG. 39.

Since upper and lower A-arms 454, 456 are connected to front leg 458through pins (or bolts) 466, 468, front leg 458 cannot rotate around itsvertical centerline. Therefore, front leg 208 cannot be used to turn ski464. Instead, a steering shaft 470 extends through a hole 472 boredthrough front leg 458. Steering shaft 470 is connected to handlebars 474through a mechanical linkage 476. As handlebars 474 are rotated,steering shaft 470 rotates in the direction of the arrow 478 shown inFIG. 40. Since steering shaft 470 is connected to ski 464 through a pinor bolt 480, as steering shaft 470 rotates, ski 464 turns.

While both of these front suspensions provide adequate control andsteering of the respective snowmobiles on which they are installed,neither provides a simple construction for a front suspension.

In the case of the trailing arm suspension, the trailing arm 444 addsadditional components to the system. The additional components add tothe manufacturing cost and to the complexity of snowmobile 12. Moreover,the additional components increase the overall weight of snowmobile 12.

In the case of double A-arm suspension 452, the same is true. In thiscase, however, the complexity of the system and the weight of thecomponents are particularly pronounced. For example, it is estimatedthat the weight of front leg 458 is about twice that of front leg 448 oftrailing arm suspension 442. This is attributable to the individualcomponents that comprise front leg 458, which is usually constructed asan aluminum extrusion. Steering shaft 470, which is typically made ofsteel and forms a part of front leg 458, is disposed through front leg458 to provide steering for snowmobile 460. Steering shaft 470 adds tothe overall weight of front suspension 452.

The complexity of front leg 458 is attributable not only to the designof the component but also to the considerable amount of machining andassembly that are required after front leg 458 is extruded. For example,hole 472 must be drilled through front leg 458 to accommodate steeringshaft 470. Moreover, three holes 482, 484, and 486 must be drilledthrough front leg 458 to accommodate upper A-arm 452, lower A-arm 454,and shock absorber 462. In addition, while not shown in the drawings, ahollow shaft is welded between the sides of front leg 458 to accommodatethe pins (such as pin 466) that connect upper A-arm 454, lower A-arm456, and shock absorber 462 to front leg 458. A bushing is usuallyplaced within the hollow shaft to facilitate pivoting motion of the pinsinserted therethrough. All of this adds considerably to the overallweight and construction cost of snowmobile 460.

In the manufacture of snowmobiles (as with the construction of anyproduct), one goal is to reduce the weight of the final vehicle. Anotherobject is to reduce the complexity of the vehicle. Both goals ultimatelyreduce the overall manufacturing cost of the vehicle.

The inventors of the present invention recognized that a hybrid approachbetween the two prior art suspensions might accomplish both of theseobjectives. Namely, a hybrid approach might provide both a moresimplified construction and a lower weight for a front suspension. Inaddition, the inventors recognized that such a hybrid approach mightprovide a front suspension that could be applicable both to snowmobiles,wheeled vehicles, ATVs, and other recreational vehicles.

No prior art front suspension, however, offers or suggests a practicableapproach.

SUMMARY OF THE INVENTION

In view of the foregoing, one object of the present invention is toexploit the design elements of a snowmobile that are easily and readilytransferred to the design of a wheeled vehicle, such as an ATV, based ona basic frame structure.

To that end, one object of the present invention is to provide a frontsuspension that incorporates a double A-arm construction which does notrequire a heavy, front leg with a steering shaft disposed therein.

It is another object of the present invention to provide a frontsuspension for a snowmobile, wheeled vehicle, or ATV that does notrequire a trailing arm.

Accordingly, it is an object of the present invention to provide a frontsuspension with a light-weight leg that is rotatable about a verticalaxis.

It is still another object of the present invention to provide asuspension for a vehicle that includes an upper A-arm and a lower A-arm.The suspension further includes a leg with a vertical axis that isrotatably connected to both the upper A-Arm and the lower A-arm. Amechanical link is rotatably connected to the leg so that movement ofthe mechanical link applies rotational force to the leg to cause the legto rotate about the vertical axis.

Another object of the present invention is to provide a suspensionfurther including a first ball joint connecting the upper A-arm to theleg, a second ball joint connecting the lower A-arm to the leg, and athird ball joint connecting the mechanical link to the leg.

A further object of the present invention is to provide a suspensionwhere the leg is an aluminum extrusion with the direction of theextrusion perpendicular to the vertical axis of the leg.

Another object of the present invention is to provide a suspension wherethe leg is squeeze-cast aluminum.

A further object of the present invention is to provide a snowmobile anda wheeled vehicle, such as an ATV, including such a suspension.

Still other objects of the present invention will be made apparent bythe discussion that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully described in conjunction with thefollowing drawings wherein:

FIG. 1 is a side-view schematic illustration of a prior art snowmobile,showing the prior art positioning of a rider thereon;

FIG. 2 is a side view illustration of the exterior of a snowmobileconstructed according to the teachings of the present invention, alsoshowing the positioning of a rider thereon;

FIG. 3 is an overlay comparison between the a prior art snowmobile (ofthe type depicted in FIG. 1) and a snowmobile constructed according tothe teachings of the present invention (as shown in FIG. 2),illustrating the difference in passenger positioning, among otherfeatures;

FIG. 4 is an exploded view of a frame assembly representative of thetype of construction typical of a snowmobile assembled according to theteachings of the prior art (specifically, the view illustrates thecomponents of a 2000 model year Ski-Doo® Mach™ Z made by Bombardier Inc.of Montréal, Québec, Canada);

FIG. 5 is a side view schematic illustration of the snowmobileillustrated in FIG. 2, with the fairings and external details removed toshow some of the internal components of the snowmobile and theirpositional relationship to one another;

FIG. 6 is a perspective illustration of a portion of the frame assemblyof the present invention, specifically the portion disposed toward therear of the vehicle;

FIG. 7 is a perspective illustration of a forward support frame, whichconnects with the portion of the frame assembly depicted in FIG. 6;

FIG. 8 is a front view illustration of an upper column of the frameassembly shown in FIG. 6;

FIG. 9 is a left side view illustration of the upper column depicted inFIG. 8;

FIG. 10 is a right side view illustration of the upper column shown inFIG. 8;

FIG. 11 is a perspective illustration, from the front left side, of atunnel portion of the frame assembly of the present invention;

FIG. 12 is another perspective illustration, from the rear left side, ofthe tunnel portion of the present invention shown in FIG. 11;

FIG. 13 is a perspective illustration, from the front left side, showingthe combination of the frame assembly depicted in FIG. 6 connected tothe tunnel portion depicted in FIGS. 11 and 12;

FIG. 14 is a perspective illustration, from the rear left side, showingthe combination of the frame assembly depicted in FIG. 6 connected tothe tunnel portion depicted in FIGS. 11 and 12 and also showing aportion of a front suspension assembly;

FIG. 15 is a perspective illustration, from the front left side, of someof the components that are part of the front suspension assemblydepicted in FIG. 14;

FIG. 16 is a perspective illustration, from the front left side, of aportion of a sub-frame that is part of the front suspension assemblyillustrated in FIG. 15;

FIG. 17 is another perspective illustration, from the front left side,of the front suspension assembly for a snowmobile, constructed accordingto the teachings of the present invention, showing the positionalrelationship between the parts illustrated in FIG. 15 and the sub-frameillustrated in FIG. 16;

FIG. 18 is a side view schematic of the frame assembly of the presentinvention showing the positional relationship between the frame assemblyand the engine, among other components;

FIG. 19 is a perspective illustration, from the left side, of the frameassembly according to the teachings of the present invention, alsoshowing the positional relationship between the frame assembly, theengine, and the front suspension;

FIG. 20 is another perspective illustration, from the front left side,of the combined frame assembly and tunnel portion constructed accordingto the teachings of the present invention, also showing the positionalrelationship between the frame assembly, the engine, and the frontsuspension;

FIG. 21 is a front perspective illustration of the embodiment depictedin FIG. 20;

FIG. 22 is a perspective illustration of a slightly different embodimentfrom the one depicted in FIG. 20;

FIG. 23 is a schematic side view illustration of the frame assembly ofthe present invention as embodied in a wheeled vehicle;

FIG. 24 is a schematic side view illustration of the frame assembly ofthe present invention as embodied in a slightly modified version of awheeled vehicle;

FIG. 25 is an enlarged side view illustration of the frame assembly ofthe present invention as embodied in the wheeled vehicle shown in FIG.24;

FIG. 26 is a perspective illustration, from the left rear, of the frameassembly of the present invention, showing some of the detail of thefront suspension incorporated into the wheeled vehicle shown in FIGS. 23and 24;

FIG. 27 is a perspective illustration, from the front left, showing theframe assembly of the present invention as depicted in FIG. 26;

FIG. 28 is a perspective illustration, from the rear left side of analternate embodiment of the frame assembly of the present invention;

FIG. 29 is a side view illustration of the frame assembly shown in FIG.28;

FIG. 30 is a top view of the frame assembly depicted in FIG. 28;

FIG. 31 is a side view illustration of the frame assembly shown in FIG.29, illustrating the variable positioning of the handlebars that ispossible with this embodiment of the present invention;

FIG. 32 is a perspective illustration of the embodiment shown in FIG.31, showing in greater detail the variations in positioning of thehandlebars that is made possible by the construction of the presentinvention;

FIG. 33 is a close-up side-view detail of the connection point betweenthe handlebars and the frame assembly of the present invention,illustrating the variable positioning of the handlebars;

FIG. 34 is a further illustration of the variable positioning feature ofthe present invention;

FIG. 35 is a graph showing the vertical displacement rate of the frameof the present invention in comparison with a prior art Bombardiersnowmobile (the ZX™ series) and a prior art snowmobile made by ArcticCat;

FIG. 36 is an exploded perspective of a trailing arm front suspensionfor the Mach 1 R™ snowmobile (model year 2000) made by Bombardier Inc.of Montréal, Québec, Canada;

FIG. 37 is a front view of a snowmobile patented in part by Arctic Catin U.S. Pat. No. 5,664,649, which illustrates a double A-arm frontsuspension typical in the prior art;

FIG. 38 is a side view a portion of the front suspension illustrated inFIG. 37, showing certain aspects of the front suspension in greaterdetail;

FIG. 39 is a front view illustration of a simplified drawing of anotherembodiment of the double A-arm front suspension of the type illustratedin FIG. 37;

FIG. 40 is a top view of the simplified drawings of the double A-armsuspension illustrated in FIG. 39;

FIG. 41 is a perspective illustration of a portion of the three-balljoint front suspension of the present invention, illustrating thelocations of the ball joints in connection with a front leg of therecreational vehicle of the present invention;

FIG. 42 is a side view illustration of the three-ball joint suspensionillustrated in FIG. 41; and

FIG. 43 is another side view illustration of the three-ball jointsuspension illustrated in FIG. 41.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before delving into the specific details of the present invention, itshould be noted that the conventions “left,” “right,” “front,” and“rear” are defined according to the normal, forward travel direction ofthe vehicle being discussed. As a result, the “left” side of asnowmobile is the same as the left side of the rider seated in aforward-facing position on the vehicle (or travelling in a forwarddirection on the vehicle).

FIG. 1 illustrates a rider operator 10 sitting on a prior art snowmobile12. Rider 10 is positioned on seat 14, with his weight distributed overendless track 16. Motor 18 (shown in general detail) is located overskis 20. As with any snowmobile, endless track 16 is operativelyconnected to motor (or engine) 18 to propel snowmobile 12 over the snow.Motor or engine 18 typically is a two-stroke internal combustion engine.Alternatively, a 4-stroke internal combustion engine may be substitutedtherefor. In addition, any suitable engine may be substituted therefor.

FIG. 2 provides a side view of a snowmobile 22 constructed according tothe teachings of the present invention. Here, rider/operator 24 is shownin a more forward, racing-like position, which is one of the aspects ofthe present invention. In this position, the weight of operator 24 isforward of the position of rider 10 in the prior art example.

The positioning of rider 24 closer to motor 36 offers several advantagesthat are not achieved by the prior art. For example, since rider 24 ispositioned closer to the engine 36, the center of gravity of rider 24 iscloser to the center of gravity of the vehicle, which is often at thedrive axle of the vehicle or near thereto. In other words, rider 24 hashis weight distributed more evenly over the center of gravity of thevehicle. As a result, when the vehicle traverses rough terrain, rider 24is better positioned so that he does not experience the same impact froman obstacle as rider 10 on snowmobile 12. The improved rider positioningillustrated in FIG. 2 also improves the rider's ability to handle thevehicle.

FIG. 2 illustrates the basic elements of snowmobile 22. Snowmobile 22includes an endless track 26 at its rear for propulsion. A rearsuspension 28 connects endless track 26 to the vehicle frame. Snowmobile22 also includes a front suspension 30. Skis 32, which are operativelyconnected to handlebars 34, are suspended from the front suspension 30for steering the vehicle. A motor or engine (preferably, an internalcombustion engine) 36 is located at the front of snowmobile 22, aboveskis 32. Operator 24 is seated on a seat 38, which is positioned abovethe endless track 26.

Three positional points of particular relevance to the present inventionare also shown in FIG. 2. Specifically, seat position 40, foot position42, and hand position 44 of operator 24 are shown. In the modifiedseating position of operator 24, which is made possible by the teachingsof the present invention, hand position 44 is forward of foot position42, which is forward of seat position 40. The three positions definethree angles, a, b, and c between them that help to define the seatingposition of operator 24 and permit rider 24 to be closer to center ofgravity 45 of the vehicle. Moreover, hand position 44 is forward ofcenter of gravity 45 of snowmobile 22.

FIG. 3 provides an overlay between prior art snowmobile 12 andsnowmobile 22 constructed according to the teachings of the presentinvention. Rider 10 (of prior art snowmobile 12) is shown in solid lineswhile operator 24 (of snowmobile 22) is shown in dotted lines forcomparison. The comparative body positions of rider 10 and operator 24are shown. As is apparent, the present invention permits theconstruction of a snowmobile 22 where the rider 24 is in a more forwardposition. Moreover seat position 40, foot position 42, and hand position44 differ considerably from seat position 46, foot position 48, and handposition 50 in the prior art snowmobile 12. In this position, the centerof gravity of operator 24 is closer to center of gravity 45 ofsnowmobile 22 than in the prior art example.

As a basis for comparison with the figures that provide the details ofthe present invention, FIG. 4 provides an exploded view of a frameassembly 52 for a snowmobile constructed according to the teachings ofthe prior art. Frame assembly 52 includes, as its major components, atunnel 54 and an engine cradle 56. As illustrated, engine cradle 56 ispositioned in front of tunnel 54. Engine cradle 56 receives motor 18.

As shown in FIG. 4, tunnel 54 is basically an inverted U-shapedstructure with a top plate 58 integrally formed with left and right sideplates 60, 62, respectively. Top plate 58 provides the surface onto withseat 14 is mounted, as would be known to those skilled in the art. Footboards 64 (of which only the left foot board is visible in FIG. 4) areintegrally formed with the side plates 60, 62 and extend outwardly,perpendicular to the plane of side plates 60, 62. Foot boards 64 providea location on which rider 10 may place his feet during operation ofsnowmobile 12. Top plate 58, side plates 60, 62, and foot boards 64 aremade of aluminum and formed as an integral structure.

FIG. 4 also shows that engine cradle 56 is connected to tunnel 54 by anysuitable means known to those skilled in the art. For example, enginecradle 56 may be welded or bolted to tunnel 54. Engine cradle includes abottom plate 66 and left and right side walls 68, 70, which are providedwith left and right openings 72, 74, respectively. Left opening 72 isprovided so that the shafts for the transmission (typically acontinuously variable transmission or CVT) may extend outwardly fromleft wall 68. The shafts that connect the engine 18 to the transmissionpass through left opening 72. A gearbox (not shown) typically isprovided on the right side of snowmobile 10. The shafts that connectengine 18 to the gearbox pass through right opening 74. Left and rightopenings 72, 74 also allow heat from engine 18 to be radiated fromengine cradle 56, which assists in cooling engine 18.

As FIG. 4 illustrates, left side wall 68 is provided with a beam 76 thatis removably connected thereto. Beam 76 may be removed during servicing,for example, to facilitate access to the engine components andperipheral elements disposed within left opening 72.

FIG. 4 also illustrates the placement of a handlebar support element 78,which connects to the rear of engine cradle 56. Handlebar supportelement 78 is generally an inverted U-shaped structure that extendsupwardly from the combined engine cradle 56 and tunnel 54. A bracket 80is positioned at the midpoint of handlebar support element 78 andprovides structural support for handlebars 82, which is used to steersnowmobile 12.

To provide an improved driver positioning, as described above, theinventors of the present invention appreciated the advantages of movinghandlebars 82 forward of the position shown in FIG. 1. To do this,however, required a novel approach to the construction of frame assembly52 of snowmobile 12. The redesign resulted in the present invention,which is described in detail below.

As illustrated in FIG. 5, snowmobile 22 incorporates a completelyredesigned frame assembly 84. Frame assembly 84 includes, among otherelements, tunnel 86, engine cradle 88, and over-arching frame elements90. As with snowmobile 12, snowmobile 22 includes a seat 94 on whichrider 24 sits while operating snowmobile 22. Tunnel 86 is connected to arear suspension 96 that contains a number of wheels 98 disposed on aslide frame 100 around which an endless track 102 rotates to propelsnowmobile 22 across the snow.

Endless track 102 is connected to engine 104 (preferably a two or fourstroke internal combustion engine) positioned within engine cradle 88.Endless track 102 is connected to engine 104 through a transmission 106,which is preferably a continuously variable transmission (or “CVT”), asis known in the art.

Two skis 108 are provided at the front of snowmobile 22 for steering.Skis 108 are connected to engine cradle 88 through a front suspension110. Front suspension 110 connects to skis 108 through a pivot joint 112on the top of skis 108. Skis 108 are operatively connected to a steeringshaft 114 that extends over engine 104. Steering shaft 114 is connected,in turn, to handlebars 116, which are used by operator 24 to steersnowmobile 22.

FIG. 6 illustrates the individual elements of rear frame assembly 84 ingreater detail. Rear frame assembly 84 includes an upper column 118,which is an inverted U-shaped structural element. If necessary, uppercolumn 118 may be reinforced with a cross-member 120, but this is notneeded to practice the present invention. A left brace 122 and a rightbrace 124 are connected to a bracket 126 above upper column 118. Abushing or bearing (or other similar element) 128 is attached to bracket126 and accepts steering shaft 114 therethrough. It also securessteering shaft 114 to rear frame assembly 84. Left and right braces 122,124 include left and right brackets 130, 132 at their lower portions.Left and right brackets 130, 132 secure left and right braces 122, 124to tunnel 86 of snowmobile 22.

It should be noted that, while the construction of frame assembly 84that is illustrated involves the use of tubular members, frame assembly84 may also be constructed according to a monocoque or pseudo-monocoquetechnique. A monocoque construction is one where a single sheet ofmaterial is attached to an underlying frame (such as with theconstruction of an aircraft). The skin applied to the frame addsrigidity to the underlying frame structure. In a similar manner, apseudo-monocoque technique provides a rigid structure by providing aframe constructed from a single sheet of material.

Instead of constructing frame assembly 84 from a number of tubularmembers, frame assembly 84 may be constructed from a single sheet ofmaterial (such as aluminum) that has been pressed or molded into theappropriate shape using a pseudo-monocoque manufacturing technique. Aswould be understood by those skilled in the art, this would result in aconstruction that has a high strength with a low weight.

FIG. 7 illustrates a forward support assembly 134 (also called fronttriangle 134), which connects to bracket 126 and extends forwardly ofbracket 126. Forward support assembly 134 includes a bracket 136 at itsrear end that connects to bracket 126 of frame assembly 84 (preferablyby welding). Forward support assembly 134 also has left and right braces138, 140 that extend forwardly and downwardly from bracket 136 and areconnected thereto preferably by welding. Left and right braces 138, 140are connected at their forward ends by a cross-member 142, whichincludes a plurality of holes 144 therein to lighten the weight thereof.Left and right connecting brackets 145, 146 are connected tocross-member 142. Left and right connecting brackets 145, 146 connect,in turn, to front suspension 110.

FIGS. 8, 9, and 10 illustrate upper column 118 in greater detail. Asdescribed above, upper column 118 is essentially an inverted U-shapedmember that is preferably tubular in shape to facilitate itsconstruction. Upper column 118 preferably is bent into the appropriateshape from a straight tube. As would be understood by those skilled inthe art, however, upper column 118 need not be made as a tubular member.

Upper column 118 has left and right legs 148, 150 that extend downwardlyfrom an apex 152. A bracket 154 is disposed at apex 152 for connectionto bracket 126 of frame assembly 84. Preferably, bracket 154 is weldedat the apex of upper column 118 (however any other suitable attachmentmeans is possible). Left leg 148 includes a bracket 156 at itslower-most portion that connects left leg 148 to engine cradle 88.Similarly, right leg 150 includes a bracket 158 at its lower-mostportion to connect right leg 150 to engine cradle 88. Preferably,brackets 156, 158 are welded to upper column 118. Left and right legs148, 150 preferably attach to engine cradle 88 via bolts or othersuitable fasteners.

FIGS. 11 and 12 illustrate tunnel 86 in greater detail. Tunnel 86includes a top plate 160 with left and right downwardly extending sideplates 162, 164. A left foot rest 166 extends outwardly from the bottomof left side plate 162. Similarly, a right foot rest 168 extendsoutwardly from the bottom portion of right side plate 164. Left andright foot rests 166, 168 provide a location along tunnel 86 onto whichrider 24 may place his or her feet while operating snowmobile 22.

Left side plate 162 extends forwardly beyond the front portion 170 oftunnel 86 to form a left engine cradle wall 172. Similarly, right sideplate 164 extends forwardly of front end 170 of tunnel 86 to form rightengine cradle wall 174. At the lower edge of left and right enginecradle walls 172, 174, there are laterally extending portions 176, 178,which serve to strengthen left and right engine cradle walls 172, 174.Removable elements 180 extend between left foot rest 166 and leftlaterally extending portion 176. Removable portions 180 may or may notbe removed between left foot rest 166 and left laterally extendingportion 176. FIG. 11 shows removable portions 180 removed, while FIG. 12shows removable portions 180 not removed. It should be noted that thesame removable portions 180 may or may not extend between right footrest 168 and right laterally extending portion 178.

Left engine cradle wall 172 preferably includes an opening 182therethrough. Opening 182 permits the shafts from transmission 106 topass therethrough. Unlike left engine cradle wall 172, right enginecradle wall 174 does not include such an opening. Instead, right enginecradle wall 174 is essentially solid. Due to its construction, rightengine cradle wall 174 reflects radiant heat from engine 104 back toengine 104 to assist in minimizing heat dissipation from engine 104.Left and right openings 184, 186 are provided through left and rightengine cradle walls 172, 174 so that a drive shaft 188 may passtherethrough. Drive shaft 186 connects to endless track 102 forpropulsion of snowmobile 22. Opening 182 may be reinforced (about itsperiphery) by reinforcing member 190, also as illustrated in FIGS. 11and 12. Left engine cradle wall 172 also includes an opening 192 aboveopening 184 through which a shaft passes for part of transmission 106.

FIGS. 13 and 14 illustrate a combination of a variation of frameassembly 190 connected to tunnel 86. Frame assembly 190 includes uppercolumn 118 as illustrated in FIGS. 8-10. However, frame assembly 190differs somewhat from frame assembly 84. For example, left and rightbraces 194, 196 are shaped so that they extend outwardly from thepositions defined by left and right braces 122, 124. As illustrated,left and right braces 194, 196 include elbows 198, 200. A cross-brace202 optionally may be placed between left and right braces 194, 196 toadd structural rigidity to frame assembly 190. As with frame assembly84, a bracket 126 is provided at apex 204 where left and right braces194, 196 meet one another. Forward support assembly 134 is the same asdepicted in FIG. 7. A front engine cradle wall 206 is also shown in FIG.13.

FIGS. 15-17 illustrate various aspects of front suspension 110 andassociated structures. While the figures illustrate the embodimentpreferably used in combination with snowmobile 22, it should berecognized that front suspension 110 may also be used in combinationwith a wheeled vehicle, as will be discussed in connection with FIGS.23-27.

Front suspension 110 includes left and right ski legs 208, 210. Left andright ski legs 208, 210 are preferably made from aluminum and arepreferably formed as extrusions. While an aluminum extrusion ispreferred for left and right ski legs 208, 210, those skilled in the artwould appreciate that ski legs could be made from any suitable materialand in any acceptable manner that would provide similar strength and lowweight characteristics. Left and right ski legs 208, 210 include holes212, 214 through which a fastener (not shown) is disposed to pivotallyconnect skis 32 to snowmobile 22, as shown in FIG. 2.

Left and right ski legs 208, 210 are movably connected to left and rightsuspension arms 216, 218. Left and right suspension arms 216, 218include lower left and right suspension support arms 220, 222 and upperleft and right suspension support arms 224, 226, preferably in the shapeof elongated cylindrical bodies.

As shown in FIGS. 15 and 17, lower left suspension support arm 220connects to left ski leg at lower left attachment point 228 preferablythrough a ball joint (not shown) so that left ski leg 208 may pivot androtate with respect to lower left suspension support arm 220. Similarly,lower right suspension support arm 222 connects to right ski leg 210 atlower right attachment point 230, preferably through a ball joint. Upperleft suspension support arm 224 preferably attaches to left ski leg 208at upper left attachment point 232, preferably through a ball joint orother suitable means. In addition, upper right suspension support arm226 connects to right ski leg 210 at upper right attachment point 234through a ball joint or other suitable means.

Lower left suspension support arm 220 includes front and rear members236, 238, which meet at apex 240 where they connect with left lowereyelet 242. Front member 236 includes a joint 244 at an inner end, andrear member 238 includes a joint 246 also at an inner end. Similarly,lower right suspension support arm 222 includes front and rear members248, 250, which meet at apex 252 where they connect with right lowereyelet 254. Front member 248 includes a joint 256 at an inner end andrear member 250 includes a joint 258 also at an inner end.

Upper left suspension support arm 224 includes front and rear members260, 262, which meet at apex 264 where they connect with upper lefteyelet 266. Front member 260 includes a joint 268 at an inner end, andrear member 262 includes a joint 270 also at an inner end. Similarly,upper right suspension support arm 226 includes front and rear members272, 274, which meet at apex 276 where they connect with upper righteyelet 278. Front member 272 includes a joint 280 at an inner end andrear member 274 includes a joint 282 also at an inner end.

At a point inward from apex 240, lower left suspension support arm 220includes a left bracket 284 that is connected to and extends partiallyalong front and rear members 236, 238. Similarly, lower right suspensionsupport arm 222 includes a right bracket 286 that is connected to andextends partially along front and rear members 248, 250. Slidablyattached to rear member 238 of lower left suspension arm 220 is a leftpivot block 288. A right pivot block 290 is slidably attached to rearmember 250 of lower right suspension support arm 222. A stabilizer bar292 is connected between left and right pivot blocks 288, 290.Stabilizer bar 292 is adapted to slide and pivot by way of left andright pivot blocks 288, 290. These blocks 288, 290 slide relative toleft and right lower suspension support arms 220, 222.

Stabilizer bar 292 helps reduces the pitching movement of the vehiclewhile cornering. While traversing uneven terain or cornering, one sideof the vehicle suspension system 295 such as that shown in FIG. 21 maycalapse, meaning the shock absorber 328 may be compressed, more than theshock absorber 326 on the oposite side of the vehicle. As left and rightsupport arms 216, 218 of the suspension system 295 are calapsedunevenly, stablizer bar 292, due to its U-shaped geometry andattachments 293 which prevents bar 292 from moving horizontally, acts asa torsion spring, preferably made of steel, forcing the support arms 216and 218 to remain relativly at the same position to the horizontalground on which the vehicle is traveling. As would be recognized by oneskilled in the art, pivot blocks 288, 290 need not be attached to thelower suspension arms 238 and 250 as in the prefered embodiment in orderto function properly. Pivot blocks 288, 290 could also be attached toany one suspension arm on support arm 216 and to any one suspension armon support arm 216.

In a situation where support arms 216 begins to calapse but support arms218 remain uncalapsed, which may occur while support arms 216 encountersunever terrain or cornering, stabilizer bar 292 will undergo a twistingmotion due to its attachment to pivot block 288. As supports arms 216continue to calapse, the twisting of stabililzar bar 292 thus increasesand at the same time stabilizer bar 292 increases the lifting forceapplied to pivot block 290 which in turn tends to raise the support arms218. Pivot blocks 288, 290 are constructed to pivot and slide alongsupport arms 216 and 218 and also to slidingly recieve stabilizer bar292. This construction allows the stabilizer bar to produce only alifting force on the support arms 218 so that it will pivot about points256, 258, 280 and 282. As would be recognized by one skilled in the art,the same sequent of events would produce the same effect if the supportarms 218 were to be calapsed to a greater extend than support arms 216.

Left and right bushings 296, 298 are provided to allow some rotation ofthe components of front suspension 110. Left and right ski legs 208, 210rotatably connect to front suspension 110 for facilitating movement ofskis 32.

FIG. 16 illustrates sub-frame 294, which is essentially a unitary,V-shaped structure. Sub-frame 294, which forms a part of frontsuspension 110, includes a central channel 300 flanked on either side byleft and right upwardly extending panels 302, 304. Left upwardlyextending panel 302 includes a left lower panel 306 connected to lefttransition structure 308 and left triangular panel 310. Similarly, rightupwardly extending panel 304 includes a right lower panel 312 connectedto right transition structure 314 and right triangular panel 316. Whilesub-frame 294 preferably is a unitary structure (an integrally-formedstructure), sub-frame 294 need not be constructed in this manner. Aswould be understood by those skilled in the art, sub-frame 294 may beassembled from a number of separate elements that are connected togetherby any suitable means such as by welding or by fasteners.

As illustrated in FIG. 17, sub-frame 294 is an integral part of frontsuspension 110 and connects to left support arm 216 and right supportarm 218 through a number of brackets 318 connected at various locationson sub-frame 294.

FIG. 18 is a side view of one embodiment of the completed frame assembly84 of the present invention. As shown, over-arching frame elements 90are connected between tunnel 86 and sub-frame 294 to establish an apex320 to which steering shaft 114 is connected.

FIG. 19 is a perspective illustration of the embodiment of the presentinvention shown in FIGS. 13 and 14 to assist in understanding the scopeand content of the present invention. As illustrated, drive shaft 322extends through left opening 182 in left engine cradle wall 172. Aportion of gearbox 324 is also visible. In addition, left shock absorber326, which is connected between cross-member 142 and left support arm216, is illustrated. Right shock absorber 328, which extends betweencross-member 142 and right support arm 218 is visible in FIG. 20.Furthermore, left forward foot wall 330 is shown at the forward end ofleft foot rest 166. A similar forward foot wall may be provided on theright side of snowmobile 22 (but is not illustrated herein).

FIGS. 20 and 21 illustrate further details of the present invention byshowing the various elements from slightly different perspective views.FIG. 22 illustrates the modified version of the elements of the presentinvention shown in FIGS. 6 and 7. Here, left and right braces 122, 124are illustrated instead of left and right braces 194, 196. As discussedpreviously, left and right braces 122, 124 differ from left and rightbraces 194, 196 in that they are not bent but, instead, are straightelements of overarching frame 90. The same left and right braces 122,124 are shown in FIG. 18. As would be understood by those skilled in theart, the two different embodiments of these braces are interchangeable.In addition, their shape may be altered depending on the requirements ofthe particular vehicle design, as would be understood by those skilledin the art.

Left and right braces 194, 196 are bent to accommodate an airbox (notshown) between them. Left and right braces 122, 124 are not bent becausethey do not need to accommodate an airbox.

FIG. 20 also illustrates steering gear box 115 at the bottom end ofsteering shaft 114 that translates the movement of handlebars 116 into asteering motion of skis 32.

FIGS. 23-27 illustrate alternate embodiments of the present inventionthat are designed for a wheeled vehicle 332, rather than a snowmobile22. For the most part, the elements designed for wheeled vehicle 332 arethe same as those for snowmobile 22, except for those elements requiredto attach wheels 334 to wheeled vehicle 332.

In the preferred embodiment of wheeled vehicle 332, the vehicle includestwo front wheels 334 and a single rear wheel 336. As would be understoodby those skilled in the art, however, wheeled vehicle 332 may beconstructed with two rear wheels rather than one. If so, wheeled vehicle332 would be a four-wheeled vehicle rather than the three-wheeledvehicle shown.

Wheeled vehicle 332 includes a seat 338 disposed over tunnel 86 in thesame manner as snowmobile 22. The vehicle includes engine 104 at itsforward end, encased by fairings 340. Fairings 340 protect engine 104and provide wheeled vehicle 332 with an aesthetically pleasingappearance. Engine 104 is connected to CVT 106, which translates thepower from engine 104 into motive power for wheeled vehicle 332.

As shown in FIG. 23, CVT 106 is connected by suitable means to driveshaft 342, which is connected to rear wheel 336 by a drive chain 344. Asprocket 346 is connected to drive shaft 342. A similar sprocket 348 isprovided on the shaft connected to rear wheel 336. Drive chain 344 is anendless chain that connects sprockets 346, 348 to one another. To stopwheeled vehicle 332 during operation, disc brakes 350 are connected tofront wheels 334. Disc brakes 350 clamp onto discs 352 to slow or stopwheeled vehicle 332 in a manner known to those skilled in the art.

A rear suspension 354 is provided under tunnel 86. Rear suspension 354absorbs shocks associated with the terrain over which wheeled vehicle332 travels. Rear suspension 354 replaces rear suspension 28 onsnowmobile 22.

FIG. 24 illustrates an alternate embodiment of wheeled vehicle 356.Wheeled vehicle 356 differs in its construction at the rear.Specifically, rear end 358 is shorter than that shown for wheeledvehicle 332. In addition, wheeled vehicle 356 includes a four strokeengine, rather than the two stroke engine 104 illustrated for wheeledvehicle 332. Also, wheeled vehicle 356 includes a manual speedtransmission 360 (with a clutch) rather than continuously variabletransmission 106, as illustrated with other embodiments of the presentinvention. Both constructions of the wheeled vehicle, as well as manyother variations, are contemplated within the scope of the presentinvention. In addition, as discussed above, the present invention may beused with a two or four stroke engine (or any other type of engine thatprovides the motive power for the vehicle).

FIG. 25 illustrates in greater detail the embodiment of the presentinvention shown in FIG. 24.

FIGS. 26-27 illustrate the basic frame assembly contemplated for wheeledvehicles 332, 356. For either vehicle, the construction of frameassembly 191 is similar to that previously described. This embodimentdiffers in that left and right wheel knuckles 366, 368 are provided sothat wheels 334 may be attached thereto. In most other respects, theconstruction of frame assembly 191 is the same as that previouslydescribed.

The variable geometry of steering shaft 364 will now be described inconnection with FIGS. 28-34.

As illustrated in FIG. 28, left brace 122 and right brace 124 extendupwardly from tunnel 370 to apex 372 where they connect to variablegeometry steering bracket 374. Upper column 118 extends from left enginecradle wall 376 and right engine cradle wall 174 and also connects tovariable geometry steering bracket 374. Forward support assembly 134extends from sub-frame 294 to variable geometry steering bracket 374.

Variable geometry steering bracket 374 is essentially a U-shaped elementwith a rear end 376 and a forward end 378. At rear end 376, a firstcross-member 380 extends between left and right legs 382, 384 ofvariable geometry steering bracket 374 to define a closed structure. Asecond cross member 386 extends between left and right legs 382, 384forward of first cross member 380 and defines a U-shaped opening 387toward forward end 378 of variable geometry steering bracket 374. Afirst pair of holes 388 and a second pair of holes 390 are disposedthrough left and right legs 382, 384 of variable geometry steeringbracket 374 and provide separate attachment points for steering shaft364. FIG. 29 illustrates the same structures in side view and FIG. 30illustrates the same structures in top view.

FIG. 31 provides another side view of the frame assembly of the presentinvention and illustrates the two positions of steering shaft 364 madepossible by the construction of variable geometry steering bracket 374.To accommodate the variable geometry of steering shaft 362 andhandlebars 116, steering shaft 364 includes a bend 402 at its lower end.Steering shaft 364 passes through a bearing or bushing (not shown) atits upper end that is connected to variable geometry steering bracket374 at either of first or second pairs of holes 388, 390. By selectingeither first or second pairs of holes 388, 390, first and secondhandlebar positions 404, 406 are selectable. As would be recognized bythose skilled in the art, however, variable geometry steering bracket374 may be provided with greater that two pairs of holes 388, 390 tofurther increase the variability handlebars 116. Also, variable geometrysteering bracket 374 may be provided with a construction that permitsinfinite variation of the position of handlebars, as would be understoodby those skilled in the art, should such a construction be desired.

FIGS. 32-34 provide additional views of the variable positioning of thehandlebars 116 to facilitate an understanding of the scope of thepresent invention.

Frame assembly 84, 190, 191 of the present invention uniquelydistributes the weight loaded onto the vehicle, whether it is snowmobile22 or one of wheeled vehicles 332, 356. Each of the main components ofthe frame assembly 84, 190, 191 forms a triangular or pyramidalconfiguration. All of the bars of the frame assembly 84, 190, 191 workonly in tension and compression, without bending. Therefore, each bar offrame assembly 84, 190, 191 intersects at a common point, the bracket126 (in the non-variable steering geometry) or variable geometrysteering bracket 374. With this pyramidal shape, the present inventioncreates a very stable geometry.

Specifically, the structure of frame assembly 84, 190, 191 enhances thetorsional and structural rigidity of the frame of the vehicle. Thisimproves handling. Usually, with a snowmobile, there is only a smalltorsional moment because the width of the snowmobile is only about 15inches. An ATV, on the other hand, has a width of about 50 inches and,as a result, experiences a significant torsional moment. Therefore, toconstruct a frame assembly that is useable in either a snowmobile or anATV, the frame must be able to withstand the torsional forces associatedwith an ATV.

Not only does frame assembly 84, 190, 191 reduce torsional bending, italso reduces the bending moment from front to rear. The increasedrigidity in both directions further improves handling.

In addition, the creation of frame assembly 84, 190, 191 has at leastone further advantage in that the frame can be made lighter and strongerthan prior art frame assemblies (such as frame assembly 52, which isillustrated in FIG. 4). In the conventional snowmobile, frame assembly52 included a tunnel 54 and an engine cradle 56 that were rivetedtogether. Because frame assembly 84, 190, 191 adds strength and rigidityto the overall construction and absorbs and redistributes many of theforces encountered by the frame of the vehicle, the panels that make upthe tunnel 86 and the engine cradle 88 need not be as strong or as thickas was required for the construction of frame assembly 52.

In the front of the vehicle, left and right shock absorbers 326, 328 areconnected to forward support assembly 134 so that the forces experiencedby left and right shock absorbers 326, 328 are transmitted to frameassembly 84, 190, 191. In the rear of the vehicle, the left and rightbraces 122, 124 are orientated with respect to the rear suspension.Upper column 118 is positioned close to the center of gravity of thevehicle's sprung weight. The sprung weight equals all of the weightloaded onto the vehicle's entire suspension. The positioning of theseelements such that they transmit forces encountered at the front, middleand rear of the vehicle to an apex creates a very stable vehicle that iscapable of withstanding virtually any forces that the vehicle mayencounter during operation without sacrificing vehicle performance.

FIG. 35 illustrates the degree to which the rigidity of a frameconstructed according to the teachings of the present invention isimproved. The test illustrated here is known as a three-point testbecause three points on the frame are held in a fixed position and afourth point is subjected to a measurable force. The displacement of theframe under a particular load is measured. The smaller the distance thatthe frame moves under a given stress, the greater is the rigidity ofthat frame.

Here, the highest line on the graph illustrates that for a 100 kg load,the vertical displacement of the frame of the present invention is only−2 mm. However, in the prior art Bombardier ZX™ model snowmobile, a loadof only 50 kg produced a vertical displacement of −6 mm. In addition, aload of about 30 kg on the frame for the prior art Arctic Cat®snowmobile produced a vertical displacement of −6 mm. In other words,the structural rigidity of the frame assembly of the present inventionis greatly improved.

Other aspects of the present invention will now be described inconnection with FIGS. 27-38.

In each of the embodiments illustrated throughout the Figures, left leg148 of upper column 118 attaches to the interior surface of right enginecradle wall 174. Right leg 150 of upper column 118 attaches to theexterior surface of left engine cradle wall 393. In this arrangement,upper column 118 may be detached from engine cradle 394 and removedeasily by sliding upper column 118 from engine cradle 394 throughC-shaped opening 392.

This embodiment of the frame assembly of the present invention differsfrom the previous embodiments in a few respects. First, left enginecradle wall 393 includes a C-shaped opening 392 instead of opening 182.C-shaped opening 392 facilitates maintenance of an engine (not shown) inengine cradle 394, because it facilitates access to the engine from theleft side, which is the side to which the engine sits within enginecradle 394. Second, an elongated radiator 396 is integrated into tunnel370. Radiator 396 includes an inlet 398 and an outlet 400 that areconnected to the cooling system of the engine to assist in reducing thetemperature of the coolant therein. To facilitate dissipation of heat,radiator 396 includes fins 402 on its underside.

Tunnel 370 and engine cradle 394 are constructed so that they form anintegral unit, once assembled. The combined tunnel 370 and engine cradle394 are essentially made up of three parts, a left side structure 408, aright side structure 410, and radiator 396. Left side structure 408 isthe combination of left engine cradle wall 393 and left side plate 162.Right side structure is the combination of right engine cradle wall 174and right side plate 164. In addition, front wall 206 and engine cradlebottom 207 also form a part of the combined structure made by tunnel 370and engine cradle 394.

Left side structure 408 and right side structure 410 are stamped from asingle sheet of metal. The rear portion of left side structure 408 isthen bent at right angles to left side plate 162 to form a left topportion 412 of tunnel 370. Similarly, the rear portion of right sidestructure 410 is bent at right angles to right side plate 164 also toform a right top portion 414 of tunnel 370. Radiator 396 extends betweenleft top portion 412 and right top portion 414 and connects left sidestructure 408 to right side structure 410.

Because left side structure 408 and right side structure 410 are stampedfrom a single sheet of metal at the same time, they are “self-aligning”.What this means is that the holes through left engine cradle wall 393and right engine cradle wall 174 are aligned with one another and do notrequire any additional reworking during the manufacture. This savesconsiderable effort in manufacture because time is not wasted trying toalign left engine cradle wall 393 with right engine cradle wall 174.

In addition, because radiator 396 connects left side structure 408 withright side structure 410 in the manner shown, additional space iscreated on tunnel 370 for a larger fuel tank 416 (shown in dotted linesin FIG. 18). As illustrated in FIG. 36, fuel tank 416 has an invertedU-shaped appearance so that it “drapes” over radiator 396. On itsbottom, tank 416 includes two downwardly-extending sections 418, 420that provide an increased fuel capacity to fuel tank 416. Depending uponthe height of radiator 396, the amount of fuel 422 that may be containedin tank 416 may be significantly increased. In the embodiment shown,height 424 is approximately 17 mm.

Because the frame assembly 84 is designed to absorb and transfer energyfor the frame, the thickness of left engine cradle wall 393 and rightengine cradle wall 174 need not be as great as was required in the priorart construction (see, e.g., FIG. 4). Specifically, the construction ofthe engine cradle 56 in the prior art required a plate thickness ofapproximately 2.58 mm. With the frame assembly 84, however, the platethickness for engine cradle 394 may be reduced to less than about 2.5mm. More preferably, the thickness my be reduced to about 2.0 mm, whichresults in a significant weight savings.

In addition, engine cradle 56 included a forward wall 57 that was anextruded element so that forward wall 57 would be thick enough andstrong enough to withstand the magnitude of forces exerted upon it. Withthe construction of engine cradle 394, however, front wall 206 does notneed to be a thick, extruded element. Instead, front wall 206 may be apiece stamped from a metal sheet, just like left side structure 408 andright side structure 410. Similarly, engine cradle bottom 207 may alsobe stamped from a sheet of metal.

The details of the front suspension of the present invention will now bedescribed in connection with FIGS. 41-43.

FIG. 41 illustrates the basic construction of a portion of frontsuspension 110 of the present invention.

FIG. 41 depicts leg 208 (or, alternatively, leg 210). Leg 208 has anessentially C-shaped body 488 with a top 490 and bottom 492. In the caseof the inclusion of front suspension 110 on snowmobile 22, ski 108 ispivotally attached to leg 208 at its bottom 492 through a bolt or pinextending through hole 494. This pivotal connection is described aboveas pivot joint 112. As would be understood by those skilled in the art,however, any pivotal connection may be employed so long as ski 108 ispermitted to pivot about an axis 496 defined by hole 494 through leg208. Leg 208 includes a front side 498 and a rear side 500, which aredefined according to the normal travel direction of snowmobile 22.

In the preferred embodiment of the present invention, leg 208 isconstructed of aluminum, which offers a light-weight construction whileproviding significant strength for the component. Leg 208 is preferablyan extrusion that has been extruded along an extrusion axis 502.Alternatively, leg 208 might be squeeze cast from aluminum. Whetherextruded or squeeze cast, leg 208 offers the strength and rigidityneeded to withstand the forces applied thereto as snowmobile 22 travelsover uneven terrain. As would be understood by those skilled in the art,however, leg 208 may be constructed from any other suitable material ormade according to a different construction technique so long as leg 208exhibits the requisite strength and rigidity. Aluminum is preferred forthe construction of leg 208 because aluminum is considerably lighter inweight than other materials such as steel. In addition, since leg 208will be exposed to a wet environment (e.g., snow and ice), aluminum alsooffers the additional benefit that it is more resistant to oxidationthan other materials such as steel.

While developing the present invention, the inventors recognized thatleg 208 cannot be made from sand-cast aluminum, because the resultingcrystallographic structure of leg 208 does not provide sufficientstrength to withstand the forces applied thereto during normal operationof snowmobile 22. Despite this, leg 208 might be sand cast from othermaterials or potentially from an alloy of aluminum that might besufficiently strong for use with the present invention.

As illustrated in FIGS. 41-43, leg 208 preferably has a waffle-likeconstruction. Specifically, leg 208 includes a number of holes 504therethrough. The exact placement and shape of holes 504 are notcritical to practice the present invention. However, there are twobenefits of holes 504 in the manufacture of leg 208. First, holes 504reduce the overall weight of leg 208. Second, when leg 208 is producedas an extrusion, holes 504 assist in the proper formation of leg 208. Itis well known in the extrusion art that the thickness of any part of theextrusion should not exceed more than about two times the thickness ofany other part. When the various parts of the extrusion are kept withinthis thickness limitation, the extrusion will form properly as itextrudes from the die on the extrusion machine.

Alternatively, leg 208 may be formed by another process in which holes504 do not extend completely therethrough. Instead, holes 504 may extendonly part of the way through leg 208. If a wall of material remains inleg 208, it may provide additional strength and rigidity to leg 208. Ofcourse, any additional material added to leg 208 will also increase itsoverall weight.

Leg 208 includes a first extension portion 506 projecting from rear side500. First extension portion 506 provides a platform through which hole508 may be drilled. Mechanical linkage 510 connects to leg 208 at hole508 through first extension portion 506. Mechanical linkage 510 connectsto a first ball joint 512, and thereon to leg 208, so that leg 208 mayrotate with respect to mechanical linkage 510 around first axis 519.

On front side 498, leg 208 includes a second extension portion 514 and athird extension portion 516. Second extension portion 514 provides aplatform through which hole 518 may be drilled. Upper A-arm 224, 226connects to leg 208 at hole 518 through second extension portion 514.Preferably, second extension portion 514 is situated at an intermediateposition between the first extension portion 506 and third extensionportion 516. Upper A-arm 224, 226 connects to a second ball joint 520,and thereon to leg 208, so that leg 208 may rotate with respect to upperA-arm 224, 226 around a second axis 522. Third extension portion 516provides a platform through which hole 524 may be drilled. Lower A-arm220, 222 connects to leg 208 at hole 524 through third extension portion516. Lower A-arm 220, 222 connects to a third ball joint 526, andthereon to leg 208, so that leg 208 may rotate with respect to lowerA-arm 220, 222 around a third axis 528.

To practice the present invention, first ball joint 512, second balljoint 520, and third ball joint 526 may be any suitable ball joint knownto those skilled in the art. All that is required is that the three balljoints 512, 520, 526 be capable of permitting leg 208 to rotate evenwhen high forces are applied thereto during operation of snowmobile 22.

In the preferred embodiment of the present invention (which isillustrated in FIG. 42), third ball joint 526 is preferably manufacturedwith a ball bearing construction, such as that made by THK of Japan. Thepreferred ball joint is made by molding a zinc housing 530 around asteel ball bearing 532 that is connected to a shaft 531. After zinchousing 530 is molded around steel ball bearing 532, the bond betweenzinc housing 530 and steel ball bearing 532 is broken mechanically. Theend result is a ball joint with an extremely well-shaped central ball.Such a construction offers a suitable ball joint for the presentinvention because significant pressure, both from the weight ofsnowmobile 22 and from the forces exerted on the joint during operationof snowmobile 22, are exerted on the ball joint. If the ball within thejoint is not smooth or very round, the joint may have a tendency tostick when significant forces are exerted thereon. This may impedesteering of snowmobile 22 under certain conditions, which, while notfatal to the operation of snowmobile 22, may have an impact on theoverall performance of snowmobile 22.

It is preferred that third ball joint 526 have a ball bearingconstruction because third ball bearing 526 is subjected to much higherforces than first ball joint 512 or second ball joint 520. Those skilledin the art, however, will readily appreciate that any suitable balljoint may be used for third ball joint 526 and that the ball jointmanufactured by THK is not required to practice the present invention.

As may be appreciated from FIGS. 41-43, in the preferred embodiment ofthe present invention, second and third axes 522, 528 are co-axial withone another. However, this is not required to practice the presentinvention. It is contemplated that second axis 522 may be offset fromthird axis 528. Similarly, in the preferred embodiment of the presentinvention, while first, second and third axes 519, 522, 528 are shownparallel to one another, it is contemplated that the three axes 519,522, 528 may be angled with respect to one another.

To steer snowmobile 22, handlebars 116 are connected to mechanicallinkage 510. Rotation of handlebars 116 causes mechanical linkage 510 toexert force on first ball joint 512 to rotate leg 208 about an axis(shown as second and third axes 522, 528). As leg 208 rotates, so doesski 108 attached to bottom 492 thereof. The axis is angled with respectto vertical from about 10°-30°, more preferably from 15°-25°, and mostpreferably 20°.

As the foregoing discussion makes clear, the present invention solvesone of the problems with the prior art. Namely, the construction offront suspension 110 provides a single leg 208 connected to an upperA-arm 224, 226 and a lower A-arm 220, 222. The three ball joints 512,520, 526 permit leg 208 to rotate about axis 522, 528. In this manner, atrailing arm 444 is not required for additional stability. Moreover, acomplex and heavy arrangement for the leg is not required, as in theArctic Cat example. Accordingly, the present invention offers a simple,light-weight construction for front suspension 110 of snowmobile 22.

Similarly, the construction of front suspension 110 may be appliedequally to a recreational vehicle such as wheeled vehicles 332, 356.However, in the case of wheeled vehicles 332, 356, leg 208 is replacedby wheel knuckles 366, 368 to which wheels 334 are rotatably attached.Since they act as supports for the skis 108 or wheels 334, or possiblyfor any other ground engaging element to which they are connected, legs208, 210 and wheel knuckles 366, 368 may be referred to generically as“supports.”

The design of leg 208 of the present invention offers at least onefurther advantage over the prior art. First, second, and third extensionportions 506, 514, 516 extend a sufficient distance from C-shaped body488 of leg 208 that the bolts or fasteners holding first, second, andthird ball joints 512, 520, 526 in place are easily accessible. Thisfacilitates replacement of one or more of the ball joints 512, 520, 526or of the leg 208, should the replacement of any of these componentsbecome necessary. In addition, the leg 208 contacts the lower A-arm 220,222 to prevent over rotation of the leg 208 which may occur when thesnowmobile is stuck and a ski is pulled on to release the snowmobile.Over rotation of the leg 208 may damage the steering shaft. The leg 208may also be locked to either the lower A-arm 220, 222 to preventsteering of the snowmobile to deter theft.

While the invention has been described by way of example embodiments, itis understood that the words which have been used herein are words ofdescription, rather than words of limitation. Changes may be made,within the purview of the appended claims without departing from thescope and the spirit of the invention in its broader aspects. Althoughthe invention has been described herein with reference to particularstructures, materials, and embodiments, it is understood that theinvention is not limited to the particulars disclosed.

1. A snowmobile comprising: a frame including a tunnel; an enginedisposed on the frame; a drive track disposed below and supported by thetunnel and operatively connected to the engine for propulsion of thesnowmobile; a front suspension including (a) at least two A-armspivotally connected to the frame, (b) a ski leg rotatably connected witha ski, the ski leg comprising: a C-shaped elongated body having aconcave side and a convex side, and a first protrusion projecting fromthe concave side, the first protrusion moveably connected to one of theat least two A-arms, a second protrusion projecting from the concaveside, the second protrusion moveably connected to the other of the atleast two A-arms, and a third protrusion projecting from a side otherthan the concave side of the C-shaped elongated body.
 2. The snowmobileof claim 1, wherein each of the first and second protrusions furtherinclude a ball joint, the A-arms moveably connected to the first andsecond protrusions through the ball joints, the ball joints defining anaxis of rotation of the ski leg passing through the first protrusion andthe second protrusion.
 3. The snowmobile of claim 1, wherein said firstand second protrusions are integral with said ski leg and said ski legis an aluminum extrusion having a direction of extrusion perpendicularto a forward direction of travel of the snowmobile.
 4. The snowmobile ofclaim 1, wherein said first and second protrusions are integral withsaid ski leg and said ski leg is an aluminum extrusion having adirection of extrusion perpendicular to one of the first protrusion andthe second protrusion.
 5. The snowmobile of claim 1, wherein said skileg further comprises at least one hole passing therethrough.
 6. Thesnowmobile of claim 2, wherein said axis is 10°to 30°from vertical. 7.The snowmobile of claim 6, wherein said axis is 15°to 25° from vertical.8. The snowmobile of claim 7, wherein said axis is 20° from vertical. 9.The snowmobile of claim 1, wherein the concave side of said C-shapedelongated body is a front side thereof defined by a forward direction ofthe snowmobile and the convex side of said C-shaped elongated body is arear side thereof defined by a rearward direction of the snowmobile. 10.The snowmobile of claim 1, wherein the third protrusion projects fromthe C-shaped ski leg such that it is parallel to the first and secondprotrusions.
 11. The snowmobile of claim 1, further comprising asteering system, the third protrusion being moveably connected to thesteering system.